Ballast resistance



Feb. 18, 1;936.- S..HAMADA BALLAST RESISTANCE Filed Nov. 28, 1935 Ihventor: Seitqku Hamada,

Patented Feb. 18, 1936 PATENT OFFICE BALLAST RESISTANCE Seitokn Ramada, Tokyo, Japan, asslgnor to General Electric Company, a corporation of New York Application November 28, 1933, Serial No. 700,091 In Japan May 30, 1933 2 Claims.

This invention relates to ballast resistances, and it has for its object the .provision of an improved device of this character wherein the current rating of the resistance is adjustable over a relatively wide range of current values.

Ballast resistors heretofore known usually comprise a resistance element, such as an iron wire, sealed into a fluid-tight envelope or tube that is filled with a suitable non-oxidizing medium such as hydrogen. As is well known, the resistance at a certain critical temperature varies with temperature so rapidly that, as the voltage across the resistance varies, the current remains practically constant; that is, after a certain temperature has been reached, the ballast resistance-will maintain a substantially constant current as the voltage across the resistance varies within a certain range.

Ballast resistors heretofore known have been designed for a specific application, 1. e., have been designed to hold a single predetermined ballasting current. Heretofore, it has been impossible to adjust these devices to vary the current ratings after they have been made. However, in some instances, the resistors may be used in parallel with shunting resistances across the load to vary the current, or with series resistors to vary the voltage rating.

Moreover, it has not been possible heretofore to make a ballast resistor that will ballast relatively small currents.

This invention, in one of its aspects, contem plates the provision of a ballast resistor which is adjustable to hold various constant currents within a rather vrlde range, and moreover, a resistor which will function to ballast a much smaller current than has been. possible heretofore.

It is another object of this invention to provide a ballast resistor that is not infiuenced'by variations in the external temperature The ballast resistor made in accordance with this invention comprises a resistance element having a balancing function, and a second resistance element having a heating function arranged in thermal relation with the ballasting resistance so as to apply heat to the ballasting resistance and thereby vary its ballasting function. Both the ballasting element and the heating element are enclosed in a fluid-tight envelope or tube which contains a relatively low pressure nonoxidizing atmosphere.

For a more complete understanding of this invention, reference should be had to the accome panying drawing in which the single figure is a view in elevation of a ballast resistance arranged in accordance with this invention, portions being broken away so as to illustrate certain details of the construction.

Referring to the drawing, this invention is shown as applied to a ballast resistance comprising a ballast resistance element 10 wound upon a suitable insulating supporting cylinder II. The resistance element It! preferably will be made of iron, but may be made of nickel, or any other suitable metal which has the desired ballasting function. I

The supporting cylinder H is supported within a suitable envelope or tube 12 which preferably will be made of glass. As shown, the cylinder l l is rigidly secured to a suitable base Ila of the tube.

Suitable means are provided for applying heat to the resistance element ID in addition to that which it receives from the current flowing through it. This auxiliary heating means comprises a resistance wire I3 which may be made of any suitable material, but preferably will be made of tungsten. The element l3, as shown, has substantially a hairpin shape, the two legs of the hairpin being received in suitable spaced parallel apertures I4 arranged longitudinally in the supporting cylinder H.

The ends of the ballast resistor Ill are connected to suitable terminal members l5 electrically connected to a pair of terminal pins IS. The ends of the resistance l3 are connected to terminal wires ll electrically connected to a pair of terminal pins I8.

It will be understood that the terminals IS of the resistance element ill will be connected in the load circuit which is to be controlled, and the terminals l8 for the resistance heating element l3 wili be connected with a suitable source of electrical supply, the voltage of which preferably will be adjustable so that the heating element can be controlled to apply different quantities of heat to the ballasting resistance l 0.

The envelope I2 is filled with a low pressure non-oxidizing atmosphere such as hydrogen.

As is well understood by those skilled in the art, when current is flowing through the resistance l0, and the resistance attains a critical temperature, the resistance varies with temperature so rapidly that, as the voltage across the resistance varies, the current remains practically constant. In other words, a" the voltage across the terminals l6 increases from zero, the resistance of the element l0 increases slowly with temperature rise in the same manner as most metals. When the lower end of the operating range is reached, the resistance of the element III increases quite rapidly with temperatures so that further increase in the voltage across the terminals l6 causes practicallyno further increase in the current. When the upper end of the operating range is reached, the resistance becomes nearly constant again. Between the lower and upper ends of the operating range the current remains substantially constant.-

If now heat is applied to the resistance element ID by the heating element IS in addition to that which the element HI receives by virtue of the current flowing through it, the lower end of the operating range will be reached when a smaller current is flowing through the resistance than would be the case if the temperature of the re sistance element l were raised solely by the current flowing through it.

Consequently, the ballast resistor ill will hold a. constant current which has a lower value when receiving heat from the auxiliary heater l3, than .when operating without the auxiliary heater.

In other words, the auxiliary heater 13 by supplying heat to the resistance l0 lowers the current value necessary to bring the temperature of the resistance to the lower end of its operating range. By controlling the heating element l3 to provide various temperatures, the resistance element Ill will ballast various constant currents, the value of the current ballasted, of course, depending upon the quantity of heat received from the auxiliary heating means l3.

As the quantity of heat imparted to the ballasting resistance element ill from the auxiliary 13 determines the working character or the ballasting resistance, that is, its current rating, it is possible, of course, to obtain this current rating in terms of the heating current or voltage supplied to the heating element 13.

It will be apparent that when the auxiliary heater l3 imparts so much heat to the resistance element III as to raise its temperature rather close to the critical value, that is, to the lower end of its operating range, a very small current will supply suflicient additional heat to cause the te:.;perature of the resistance to rise to the critical value. In other words, it is possible to ballast a very small currentwlth the ballast resistor arranged in accordance with this invention. It has been iqvoa sov round experimentally that whereas the minimum current that can be maintained. by ballasting resistors heretofore generally known is about 100 milliamperes, the ballasting' resistor of this invention will ballast a current as small as a few milliamperes.

It is to be noted also that the ballasting resistor arranged in accordance with this invention is not influenced by changes in the external temperature, because these changes affect both the ballasting resistance wire and the heating resistance element; it has been found thatthe current rating of the ballasting resistor does not vary substantially even though the external temperatures change considerably.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent oi the United States, is:-

l. A ballast resistance-comprising an insulating rod having a plurality of longitudinal openings extending therethrough, supporting means for said rod arranged at one end thereof, a ballasting resistance element wound on said rod and having terminals adjacent to said end, and means for maintaining said resistance element at a predetermined elevated temperature comprising a resistance heating element in each of said openings, said heating elements having terminals at said one end of the rod and being connected together at the opposite end thereof.

2. A ballast resistance comprising a fluid tight envelope containing a non-oxidizing atmosphere, an insulating rod, means secured to one end of said rod for supporting the same in said envelope. a ballasting resistance element wound on said rod and having both ends terminating at said end of the rod, and a heater for said resistance element comprising an elongated loop, said rod being provided with longitudinal openings receiving the sides of said loop, the terminals of the loop extending from the said end of the rod.

SEITOKU HAMADA. 

